chore: handle undefined hmr (#831)

src/client/app/data.ts

@@ -31,8 +31,10 @@ export const siteDataRef: Ref<SiteData> = shallowRef(
 
 // hmr
 if (import.meta.hot) {
-  import.meta.hot!.accept('/@siteData', (m) => {
+  import.meta.hot.accept('/@siteData', (m) => {
+    if (m) {
       siteDataRef.value = m.default
+    }
   })
 }